Glass container having an inkjet printed image and a method for the manufacturing thereof

ABSTRACT

A glass container has an outer glass surface with an inkjet printed image provided on the surface. A cold-end coating (CEC) with a thickness between 0 to 20 nm is present between the outer glass surface and the inkjet printed image. Such glass container is preferably a one-way beverage bottle. A method of inkjet printing an image on a glass container comprises the steps of (a) manufacturing a glass container having a CEC layer; (b) removing at least part of the CEC layer to a level wherein the remaining CEC layer has a thickness of 0 to 20 nm; and (c) inkjet printing an image on the glass container.

FIELD OF THE INVENTION

The present invention relates to glass containers, in particular glassbottles, decorated with printed images on the glass surface. Further,the present invention relates to a method for manufacturing such glasscontainers.

BACKGROUND OF THE INVENTION

It is commonly known in the art that beverage bottles bear a lubriciousand protective transparent coating, the so-called cold-end coating(CEC), at the outer surface. Such CEC prevents the glass container frombeing scratched and protects it in abrasive or caustic environment. TheCEC, typically a polyethylene wax causes the glass surface to becomeslippery. The resulting low friction coefficient diminishes the forcesin bottle-to-bottle contact in bottling lines and transport. Bottlescoated in this way move freely through inspection and filling lines andsustain less surface damage. A damaged surface looks bad to the consumerand weakens the glass, often resulting in premature breakage. Inaddition, instead of accepting an increase in bursting pressure, thebottle may be made lighter while still retaining its strength.

Nowadays in glass container manufacturing a two-step coating is appliedin order to obtain scratch resistance and slipperiness of the glasscontainers. In the first step, the so called hot-end coating (HEC) istypically applied by means of chemical vapor deposition (CVD) of a metalcontaining compound on the freshly formed, hot and single or double linepositioned glass containers. Such a HEC is based on coating precursorthat includes tin, titanium other heat decomposable metallic ororganometallic compounds. This application is done inside a so calledcoating tunnel or coating hood where the HEC is applied by chemicalvapor deposition in forming a thin layer of a metal oxide, for exampletin oxide. The objective is to coat the outside of the glass containerwith a homogenous even layer except for the so called finish. Since thisis done in vapor phase and on single line conveyed glass containers, arelatively homogeneous distribution can be achieved easily. The thinlayer of metal oxide, often tin oxide, is the basis for the secondcoating, the so called cold-end coating (CEC). After the HECapplication, the glass containers are usually submitted through aspecial type of oven called also annealing lehr. Latter is designedspecifically for annealing glass and to cool down the containers in acontrolled way. The glass is heated to the annealing point and thenslowly cooled down. This process relieves the internal stresses, makingthe glass much more durable.

In a subsequent process step, images of the logo, ingredients, etc.corresponding the content of the bottle are typically printed on theCEC, e.g. by screen printing.

However, a main problem is that in all industries, in particularpackaging industry, printing is continuously moving towards digitizationwith greater speed, quality, flexibility and efficiency. Unfortunately,screen printing is not a digital printing technique, as for exampleinkjet printing is. Also offset and flexographic printing systems arebeing increasingly replaced for printing applications by industrialinkjet printing systems due to their flexibility in use, e.g. variabledata printing, and due to their enhanced reliability, allowing theirincorporation into production lines.

In inkjet printing, tiny drops of ink fluid are projected directly ontoan ink-receiver surface without physical contact between the printingdevice and the ink-receiver. The printing device stores the printingdata electronically and controls a mechanism for ejecting the dropsimage-wise. Printing is accomplished by moving a print head across theink-receiver or vice versa or both.

When jetting the inkjet ink onto an ink-receiver, the ink typicallyincludes a liquid vehicle and one or more solids, such as dyes orpigments and polymers. Ink compositions can be roughly divided in:water-based, the drying mechanism involving absorption, penetration andevaporation; solvent-based, the drying primarily involving evaporation;oil-based, the drying involving absorption and penetration; hot melt orphase change, in which the ink is liquid at the ejection temperature butsolid at room temperature and wherein drying is replaced bysolidification; and energy-curable, in which drying is replaced bypolymerization induced by exposing the ink to a radiating or thermalenergy source.

The first three types of ink compositions are more suitable for anabsorbing receiving medium, whereas hot melt inks and energy-curableinks can also be printed on non-absorbing ink-receivers. Due to thermalrequirements posed by hot melt inks on the substrates, especiallyradiation curable inks have gained the interest of the packagingindustry.

However, inkjet printing on glass containers which need a CEC duringmanufacturing for the reasons mentioned above, such as bottles, has beenproven still to be difficult and to result in poor image quality of theprints.

As a result, there remains a need for optimized inkjet printing methodsfor glass containers which need a CEC, especially in high speedprocesses such as beverage bottling lines.

SUMMARY OF THE INVENTION

The present invention is directed to a glass container having an outerglass surface with an inkjet printed image provided on said surface,characterized in that a CEC with a thickness between 0 to 20 nm ispresent between the outer glass surface and the inkjet printed image.

In an embodiment in accordance with the present invention, the glasscontainer has an outer glass surface with an inkjet printed imageprovided on said surface, characterized in that the glass container hasan internal burst pressure of at least 7 bar, and in that no CEC, or aCEC with a thickness of less than 20 nm is present between the outerglass surface and the inkjet printed image.

Such glass container is preferably a one-way beverage bottle.

In addition, the present invention is directed to a method of inkjetprinting an image on a glass container comprising the steps of:

-   a) manufacturing a glass container having a CEC layer;-   b) removing at least part of the CEC layer to a level wherein the    remaining CEC layer has a thickness of 0 to 20 nm;-   c) inkjet printing an image on the glass container.

In an embodiment in accordance with the present invention, the methodcomprises the steps of:

-   a) manufacturing a glass container having an at least partially    water soluble CEC layer;-   b) removing at least part of the CEC layer to a level wherein the    remaining CEC layer has a thickness of 0 to 20 nm by rinsing the CEC    from the glass container with water and blowing the water from the    container by means of a pressurized air stream,-   c) inkjet printing an image on the glass container.

DETAILED DESCRIPTION OF THE INVENTION

It is now recognized that the reasons why ink-jet printing on glasscontainers which need a CEC has been proven still to be difficult and toresult in poor image quality of the prints, are the following:

First, it is believed, without being bound by any theory, that the CECmight interfere with bonding of inkjet inks and adhesion at the glasssurface.

Secondly, since the containers are positioned in several rows uponleaving the cooling oven, the application of CEC happens by spray gun orguns which move parallel between the respective rows of the containers,positioned above or just between the rows at shoulder height of thecontainers. Such spray pattern leads automatically to an inhomogeneousdistribution of coating material.

Although WO2013167558 describes an improved method for applying a CECintegrated in glass container manufacturing process, the methoddisclosed therein can only be applied in a single line conveyer beltconfiguration and not in a traditional and widely used multi-row massconveyer belt configuration.

Thirdly, for a good ejecting ability and fast inkjet printing, theviscosity of inkjet inks is typically much lower as compared to e.g.screen printing inks. Without being bound by any theory, lower viscosityof the inkjet ink exhibits higher mobility on a surface to be printedand higher dependency on the homogeneity of the surface. The poor imagequality of the prints might thus be a result of the high mobility of thelower-viscous inkjet inks before solidification by e.g. evaporationand/or polymerization, and the inhomogeneous distribution of CECmaterial as described here above. I.e. the lower-viscous and mobileinkjet ink droplets have the tendency to wet and move to surface regionswith a higher surface energy resulting in print defects.

It was now unexpectedly found that by removing at least part of the CEClayer of the glass substrate to a level wherein the remaining CEC layerhas a thickness of 0 to 20 nm, or is substantially completely removed,adhesion as well as print quality of the prints, e.g. color aberrationsand resolution is significantly improved compared to print quality on aglass substrate from which the CEC was not at least partially removed.Without being bound by any theory, the assumed reason for an improvedprint quality is that by removing at least part of the CEC layer to alevel wherein the remaining CEC layer has a thickness of 0 to 20 nm, thesurface homogeneity is increased and results in a reduced tendency ofthe mobile and lower-viscous inkjet inks to move on the surface beforesolidification

In a first embodiment, the present invention provides a glass containerhaving an outer glass surface with an inkjet printed image provided onsaid surface, characterized in that a CEC with a thickness between 0 to20 nm is present between the outer glass surface and the inkjet printedimage. A thickness of 0 to 20 nm is equivalent to a few monolayers orless. Preferably, the thickness of the CEC is between 0 and 10 nm, andeven more preferably between 0 and 5 nm, and most preferably the CEC iscompletely removed.

In an embodiment in accordance with the present invention, the glasscontainer has an outer glass surface with an inkjet printed imageprovided on said surface, characterized in that the glass container hasan internal burst pressure of at least 7 bar, and in that no CEC, or aCEC with a thickness of less than 20 nm is present between the outerglass surface and the inkjet printed image.

As explained above, a CEC provides increased scratch protection andimproves durability, appearance, and internal burst pressure of theglass container. By printing on glass containers which had a CEC duringprocess steps preceding printing and removing that CEC, or part of it,just before the printing step, a glass container is obtained that, afterbeing exposed to the printing step, still has an internal burst pressureof at least 7 bar, or at least 8 bar, or at least 9 bar.

Further, an embodiment may be provided wherein a HEC may be presentbetween the outer glass surface and the CEC or between the outer glasssurface and the inkjet printed image. In the latter case, CEC is removedand has a thickness of 0 nm or substantially 0 nm.

Without being bond to any theory, the excellent print quality onsubstrates in which a HEC is present between the outer glass surface andthe inkjet printed image may be explained by the homogeneousdistribution of the HEC since the HEC is usually applied in vapor phaseand on single line conveyed glass containers as explained here above.

The HEC typically comprises a metal oxide layer, typically a layer of 5to 20 nm. More specifically, said metal oxide in the metal oxide layermay be chosen from the group comprising: tin oxide, titanium oxide,zirconium oxide and/or combinations thereof, as described in U.S. Pat.Nos. 3,952,118 and 489,816.

In a particular embodiment in accordance with the present invention, themetal oxide layer of the HEC may be a tin oxide obtained frommonobutyltinchloride (MBTC) as a precursor.

Typical examples of CECs applied on glass containers may bepolyethylene, partially oxidized polyethylene, polyglycols, oleic acidor stearate based coatings.

In an embodiment of a glass container of the present invention, the CECmay be at least partially water soluble between 20 and 90° C.,preferably at 40° C. Besides benefits in the production of inkjetprinted glass containers as will be explained further in this text, anat least partially water soluble CEC may be beneficial for recyclingone-way glass container waste since it can be removed at least partiallyby rinsing with water between 20 and 90° C., preferably at 40° C.

In the context of the present invention, the CEC being at leastpartially water soluble is understood as the CEC being removed at leastpartially by technical water, tap water, purified water or distilledwater such that the bottle's slip angle increases with at least 6° afterwashing vs. before washing. Slip angles are determined by putting onebottle on top of two horizontal bottles of the same type, in linecontact. The tilt angle is increased at a certain speed and the tiltangle on which the top bottle starts to slide off is called the slipangle. A slip angle may have value of more than 30° to less than 10°.

In particular, the at least partially water soluble CEC may be fattyacid based, preferably stearate based. In another particular preferredembodiment, the at least partially water soluble CEC may be polyethyleneglycol based.

In another embodiment of a glass container of the present invention, theCEC may be at least partially oxidized by flame, corona, or plasmatreatment. It is known in the art that organic screen printing inks donot adhere well to glass containers having been treated with CEC, andthat flame, corona or plasma energy may be applied to the glasscontainers to achieve better adhesion of an organic coating (e.g. aninkjet ink) thereto.

Further, a glass container according to the present invention maycomprise a silicon containing layer, preferably a silica containinglayer (eg. pyrosil), between the CEC and the inkjet printed image. Suchsilicon containing layer provides increased bonding sites for the inkjetprinted layer(s). Furthermore, they may result in a rough nano-porousmaterial surface for increased adhesion and a surface with a highersurface energy. It may be deposited for example by flame pyrolysis.Precursors may be delivered as a vapor, an atomized liquid, an atomizedsolution, and/or the like.

A primer layer may be present between the outer glass surface and theinkjet printed image in order to enhance adhesion of the ink, i.e. onthe CEC or on the HEC, or on a silica containing layer (eg. pyrosil).Such primer may be pigmented, white or transparent and may comprise anadhesion promotor. Such primer may also be oxidized by flame, corona, orplasma treatment to enhance adhesion of the inkjet ink. A whitepigmented primer, typically containing e.g. titanium dioxide, ispreferably used to enhance the contrast and the vividness of color inksprinted on a primed substrate. This is especially effective when thesubstrate is transparent. In particular, the primer may comprise aradically reactive group moiety such as a thiol group, an amine group,or an ethylenically unsaturated group such as a vinyl ether, a vinylester, an acrylamide, a methacrylamide, a styril, or preferably anallyl, an acrylate, or a methacrylate.

The inkjet printed image on a glass container according to the presentinvention may comprise one or more layers of ink, preferablyenergy-cured ink, i.e. the ink may be cured in any suitable manner, forexample, radiation-cured by any suitable type of radiation like, forinstance, ultraviolet, electron beam, or the like, or thermally-cured byconvection oven, infrared lamps, or the like, or a combination of bothradiation and thermal energy.

On the inkjet printed glass container, a protective layer and/or a clearcoating may be applied for protecting the image and/or achieving a moreglossy or mat impression (or another optical effect).

The inkjet printed image may have a printing resolution of at least 300dpi.

After printing, a friction coefficient reduction coating may applied onthe entire glass container.

A glass container in accordance with the present invention may be aglass bottle, preferably a beverage bottle and most preferably a one-waybeverage bottle. A returnable glass container which is exposed tocaustic rinses after use, would lack HEC after a limited number ofreturns.

Further, a glass container in accordance with the present invention maybe preferably cylindrical bottle.

In an additional aspect of the present invention, an embodiment isprovided of a method of inkjet printing an image on a glass containercomprising the steps of:

-   a) manufacturing a glass container having a CEC layer;-   b) removing at least part of the CEC layer to a level wherein the    remaining CEC layer has a thickness of 0 to 20 nm;-   c) inkjet printing an image on the glass container.

Removing the CEC to level wherein the remaining CEC has a thickness of 0to 20 nm of CEC is equivalent to a few monolayers or less. Preferably,the thickness of the remaining CEC is between 0 and 10 nm, and even morepreferably between 0 and 5 nm.

In a preferred embodiment of the present invention, the CEC may be atleast partially water soluble and can be at least partially removed byrinsing with tap water, technical water, purified water or distilledwater. Depending on the rinsing time and temperature, the level ofremaining CEC may then be varied or optimized from less than 20 nm totwo or one monolayers, or to a level that only separated traces remainon the surface, or up to complete removal.

Techniques for removing a non-water soluble CEC may be chemical etching,sand blasting, dissolving in organic solvent, flame or plasmatreatments, etc.

In a specific embodiment of a method of the present invention, rinsingthe CEC for at least partially removing it from the glass container maybe performed with technical water, tap water, purified water ordistilled water at a temperature between 20° C. and 90° C., preferablyat 40° C. Rinsing time may vary between 0.1 and 15 seconds, or between0.1 and 10 seconds depending on the level of removal of the CEC.

After rinsing, the rinsed glass container may be dried by removing waterin a predominantly liquid phase, for example by blowing away the waterdroplets or by centrifuging the bottles. It was unexpectedly found thatby actively removing water in liquid state (i.e. avoiding drying), theadhesion as well as print quality of the prints, e.g. color aberrationsand resolution is significantly improved compared to print quality on aglass substrate from which the CEC was at least partially removed byrinsing and subsequently dried. Without being bound by any theory, theassumed reason is that water stains left after drying may increase thetendency of the mobile and lower-viscous inkjet inks to move on thesurface before solidification.

In a particular embodiment in accordance with the present invention, themethod comprises the steps of:

-   a) manufacturing a glass container having an at least partially    water soluble CEC layer;-   b) removing at least part of the CEC layer to a level wherein the    remaining CEC layer has a thickness of 0 to 20 nm by rinsing the CEC    from the glass container with water and blowing the water from the    container by means of a pressurized air stream,-   c) inkjet printing an image on the glass container.

Preferably, water is blown from the container's out surface by means ofa laminar flow of pressurized air.

For blowing water (droplets) from a rinsed glass container, airmanifolds may be used consisting of a closed section of pipe connectingto an air supply. Small holes are provided along the length of the pipe.Air passes through the holes and is directed at the bottles or cans inan effort to blow off the rinsing liquid. Also flat air nozzles may beused, which in fact is also a closed section of pipe, but the smallholes are replaced by a number of flat nozzles.

For reasons of increased efficiency, noise reduction, and reduced airand energy consumption, preferably air knives (also called air blades)may be used, or an air knife assembly consisting of at least one andpreferably two or more air knives. An industrial air knife is apressurized air plenum containing a series of holes or continuous slotsthrough which pressurized air exits in a thin line in a laminar flowpattern. The exit air velocity then creates an impact air velocity ontothe surface of the bottle. The thin line of air can be carefullypositioned with respect to pitch, roll and yaw angles to accuratelystrike the bottles as they pass in front of the knife to dewater an areawhere printing is to occur.

The air knifes may be positioned immediately adjacent the ink jet printhead.

Preferably the air knife (or knives) may be positioned pointing upstreamof the position at which is are located, and the air emitted therefromstrikes the bottles prior to the bottles reaching the air knife.

Further, the air knife may be positioned such that the linear air flowstrikes the upper area to be dewatered and forces the water downwardly.As a bottle moves toward the air knives, the increasing air pressurecontinues to push the liquid downwardly and off the bottle.

In a particular embodiment in accordance with the present invention, theCEC is removed to a level that increases the slip angle of the glassbottle with at least 6°, or at least 10°, or even at least 20°. Slipangles are determined by putting one bottle on top of two horizontalbottles of the same type, in line contact. The tilt angle is increasedat a certain speed and the tilt angle on which the top bottle starts toslide off is called the slip angle. A slip angle may have value of morethan 30° to less than 10°.

In case the CEC is completely removed, the HEC may be the surface onwhich the image is ink jetted.

Alternatively, in an embodiment in accordance with the presentinvention, a method of inkjet printing an image on a glass container isprovided, wherein a primer layer is applied on the glass container afterat least partial removal of the CEC and prior to inkjet printing animage on the glass container. Such primer may be pigmented, white ortransparent and may comprise an adhesion promotor. Such primer may alsobe energy-curable such that the inkjet ink can be jetted onto the wetprimer, wherein the inkjet ink has a viscosity that is lower than theprimer viscosity, and wherein the primer and the inkjet ink can besimultaneously energy-cured. Such primer may be pigmented, white ortransparent and may comprise an adhesion promotor. Such primer may alsobe oxidized by flame, corona, or plasma treatment to enhance adhesion ofthe inkjet ink. A white pigmented primer, typically containing e.g.titanium dioxide, is preferably used to enhance the contrast and thevividness of color inks printed on a primed substrate. This isespecially effective when the substrate is transparent. In particular,the primer may comprise a radically reactive group moiety such as athiol group, an amine group, or an ethylenically unsaturated group suchas a vinyl ether, a vinyl ester, an acrylamide, a methacrylamide, astyril, or preferably an allyl, an acrylate, or a methacrylate.

The remaining CEC, or in case of complete removal of CEC, the HEC or theprimer layer may be at least partially oxidized by flame, corona, orplasma treatment in order to enhance adhesion of the inkjet ink thereto.

In a further embodiment in accordance with the present invention, afterthe flame, corona, or plasma treatment, a silicon based, preferablysilica based (e.g. pyrosil) layer may be applied on the glass container.So, this silicon based layer may be applied on at least partiallyoxidized remaining CEC, on at least partially oxidized HEC, or on atleast partially oxidized primer before inkjet printing the image. Suchsilicon containing layer provides increased bonding sites for the inkjetlayer(s). Furthermore, they may result in a rough nano-porous materialsurface for increased adhesion and a surface with a higher surfaceenergy. It may be deposited for example by flame pyrolysis. Precursorsmay be delivered as a vapor, an atomized liquid, an atomized solution,and/or the like.

Preferably, glass containers manufactured according to a method of thepresent invention are filled after inkjet printing the image thereon inorder to avoid damage to the inkjet printer due to accidental burstingof the filled glass container.

In the step of inkjet printing, the inkjet print head may scan back andforth in a longitudinal direction across the moving glass container, andthe inkjet print head may not print on the way back. However,bi-directional printing may be used and may be preferred for obtaining ahigh area throughput on big size glass containers. Another preferredprinting method may print also in multiple passes but in a transversaldirection (circular around the bottle). In this method, the relativeposition of the bottle versus the printhead can be changed after everypass in order to print images that are larger than the size of one printhead. This necessitates stitching of the print artwork. Anothervariation on this method uses relative movement of the bottle vs theprinthead while printing the different passes: one obtains spiralprinting across the bottle. In the latter, stitching defects will beless pronounced. Another preferred printing method may be by a “singlepass printing process”, which can be performed by using wide inkjetprint heads or multiple inkjet print heads which cover the entire widthof the image to be printed (staggered or connected to each other). In asingle pass printing process the inkjet print heads usually remainstationary and the substrate surface is transported under the inkjetprint heads.

Inkjet printing techniques as used in the present invention may bepiezoelectric inkjet printing, continuous type and thermal,electrostatic and acoustic drop on demand type.

A preferred jetting temperature is between 10 and 70° C., morepreferably between 20 and 60° C., and most preferably between 25 and 45°C.

Non curing solvent or water-based inkjet inks may be used, butpreferably energy-curable inkjet ink is used. Radiation curable inkjetink, can be cured by exposing to actinic radiation and/or by electronbeam curing. Preferably the radiation curing is performed by an overallexposure to actinic radiation or by an overall electron beam curing.Thermally curable inkjet ink can be cured by convection oven, infraredlamps, or the like.

The curing means may be arranged in combination with the print head ofthe inkjet printer, travelling therewith so that the inkjet ink isexposed to curing energy very shortly after been jetted. In such anarrangement it can be difficult to provide a small enough energy sourceconnected to and travelling with the print head. Therefore, a staticfixed energy source may be employed, e.g. a source of curing UV-light,connected to the radiation source by means of flexible radiationconductive means such as a fiber optic bundle or an internallyreflective flexible tube. Alternatively, the actinic radiation may besupplied from a fixed source to the print head by an arrangement ofmirrors including a mirror upon the print head.

The source of radiation arranged not to move with the print head, mayalso be an elongated radiation source extending transversely across theink layer(s) to be cured and adjacent the transverse path of the printhead so that the subsequent rows of images formed by the print head arepassed, stepwise or continually, beneath that radiation source. Theradiation source is preferably an ultraviolet radiation source, such asa high or low pressure mercury lamp containing optional slopingelements, a cold cathode tube, a black light, an ultraviolet LED, anultraviolet laser or a flash light.

Furthermore, it is possible to cure the inkjet printed image using,consecutively or simultaneously, two light sources of differingwavelength or illuminance. For example, the first UV-source can beselected to be rich in UV-A, e.g. a gallium-doped lamp, or a differentlamp high in both UV-A and UV-B. The second UV-source can then be richin UV-C, in particular in the range of 260 nm-200 nm. The use of twoUV-sources has been found to have advantages e.g. a fast curing speed.

For facilitating curing, the inkjet printer often includes one or moreoxygen depletion units. The oxygen depletion units place a blanket ofnitrogen or other relatively inert gas (e.g. CO2), with adjustableposition and adjustable inert gas concentration, in order to reduce theoxygen concentration in the curing environment. Indeed, oxygen can actas a radical scavenger, taking away available radicals from thepolymerization reaction. Residual oxygen levels are usually maintainedas low as 200 ppm, but are generally in the range of 200 ppm to 1200ppm.

In the context of the present invention, the image to be inkjet printedmay comprise any type of picture, logo, text, graphic art, coding(QR-code, barcode) and the like.

EXAMPLE

Materials and Procedures:

Bottle Samples:

Bottles A: Unprinted Victoria 12 oz bottles (amber glass) were purchasedfrom Nueva Fábrica Nacional de Vidrio, S.A. de C.V. (Mexico). Thesebottle were produced with a partially water soluble CEC based on ARCOSOLM-70 commercially available from ARCO, S.A. de C.V. (Mexico).

Bottles B: Unprinted one-way 33CI Adriaan brown bottles were purchasedfrom Ardagh. These bottles were produced with a water non-soluble CECbased on RP 40 commercially available from Arkema.

Bottle Rinsing:

The bottles were rinsed with distilled water for 10 seconds at roomtemperature. The bottles were successively blow-dried with compressedair.

Slip Angle:

Slip angle measurements were performed with a Tilt Table commerciallyavailable from Agr International, Inc. The angle speed was set at3.6°/sec. For each condition, the slip angle was measured for 9 bottlesand the average slip angle value was calculated.

Printing:

Inkjet-printing of the bottles were performed on a “Laboratory Unit”commercially available from CURVINK by (Netherlands) equipped with aflaming lab module and a primer application lab module. Followingprocedure was followed for printing the bottles:

The bottles were flamed with the flaming lab module using a speed of 250mm/sec. The bottles were successively coated in the flaming lab modulewith pyrosil (commercially available from Sura Instruments). A 0.2%pyrosil concentration was used and the pyrosil speed was set at 250mm/s. The bottles were removed from the flaming lab module and cooleddown under ambient conditions at room temperature. The bottles weresuccessively coated with the primer application lab module using aalkoxy silane—based primer in a 2-revolution mode. The bottles weredried under ambient conditions during 8 minutes. The bottles weresuccessively placed in the inkjet module and the bottle body was inkjetprinted with a UV-curable acrylic-based white ink. The white ink wasjetted with a GS12 XAAR 1001 head in a single pass mode using grey scalelevel 5. A uniform full white design as well as text was printed. Thepinning level was set at 1% and was performed with a 8W LED bar fromHoenle. Finally, the bottles were taken out of the inkjet module andfully cured with a UV-bulb in an 8 rotation mode.

Pasteurization Simulator:

In order to simulate a pasteurization process, the bottles were placedin a water bath. The following temperature program was followed: 10minutes at 45° C., 20 minutes at 62° C. and 10 minutes at 30° C. Thebottles were removed from the water bath and dried in ambientconditions.

Line Simulator:

For each condition, 28 bottles were placed in a line simulatorcommercially available from Agr International, Inc. This simulates theconditions a bottle undergoes in a packaging line. The followingsettings were selected: water faucet on; abrader plate+height at EFG-2;speed control at 8 (60 rpm); gate pressure at 40% slippage (36 rpm forbottles). The bottles were placed during 30 minutes in the linesimulator and inspected visually for potential damages to the art work.

Results:

The slip angle of Bottles A and B was measured before and after bottlerinsing. For bottles B: a slip angle of 14° was found before rinsing and15° after rinsing. For bottles A: a slip angle of 5° was found beforerinsing and 27° after rinsing. Bottles A and B were printed according tothe above mentioned printing procedure with or without previous rinsingstep. It was found that the print quality of the prints on Bottles A wasbetter than the print quality of the prints on bottle B. Especially theprinted text showed more print defects on Bottle B than on Bottle A. Thebottles were successively placed in a pasteurization simulator, linesimulator, and visually inspected. It was found that the printed artworkon bottles B showed much more damages than the printed artwork onbottles A.

The invention claimed is:
 1. A method of inkjet printing an image on aglass container comprising the steps of: (a) providing a glass containerhaving a cold-end coating (CEC) layer, wherein the CEC layer is at leastpartially water soluble; (b) removing part of the CEC layer to a levelwherein the remaining CEC layer has a thickness of up to 20 nm byrinsing the CEC from the glass container with water; (c) blowing thewater from the container by means of a pressurised air stream; and (d)inkjet printing an image on the glass container; said glass containerhaving an internal burst pressure of at least 7 bar after being exposedto the printing.
 2. The method according to claim 1, comprising the stepof applying a primer layer on the glass container after at least partialremoval of the CEC and prior to inkjet printing an image on the glasscontainer.
 3. The method according to claim 1, comprising the step ofapplying a protective layer and/or clear coating on top of the inkjetprinted image.
 4. The method according to claim 1, wherein the CEC fromthe glass container is rinsed with water at a temperature between 20° C.and 90° C.
 5. The method according to claim 1, wherein removal of theCEC increases the slip angle of the glass container with at least 6°. 6.The method according to claim 1, comprising the steps of filling thecontainer with a liquid, preferably a beverage after inkjet printing theimage thereon.
 7. The method according to claim 1, wherein the remainingCEC layer has a thickness of up to 10 nm.
 8. A glass container having anouter glass surface with an inkjet printed image provided on saidsurface, wherein a cold-end coating (CEC) with a thickness up to 20 nmis present between the outer glass surface and the inkjet printed image;wherein said glass container is obtained by a method according to claim1.